Provided it's a upgrade disc that you've got, and it qualifies as version (the right version of Vista to 7)and your not trying to upgrade 32bit to 64bit, then go ahead. Now done it four times and never had a problem. But it can take a few hours depending on what you've got installed, with long periods of seeming inactivity. Be patient.
UK's best mobile network 2016: best 3G, best 4G, best mobile networks revealed